Exercising of the upper torso necessarily involves movements of the upper limbs which in turn involves the upper torso muscles and, importantly, the wrist, elbow and shoulder joints.
The upper torso muscles include the larger muscle groups such as the pectoralis major and minor, deltoids, latissimus dorsi, triceps, biceps, trapezius, teres major and several smaller muscle groups such as the infraspinatus, supraspinatus, splenius capitis, rhomboideus minor and major, levator scapulae, etc. Exercise of the upper torso muscles most commonly involves extensive use of the upper limbs, inasmuch as each of the larger muscle groups is directly or indirectly connected at one of their respective ends to the upper end of the humerus or an element of the glenohumeral joint (shoulder joint) in general.
The shoulder joint includes, among other elements, the head of the humerus which is a typical ball, and which is cradled in the glenoid fossa of the scapula. The glenoid fossa is shallow and more flat than concave, such that it presents a much smaller articular surface than the head of the humerus. The fossa is widened and slightly deepened by a rim of fibrocartilage, known as the glenoidal labrum, so that the construction of the shoulder ball and socket joint favors a wide range of movement of the arm relative to the body proper, but at the expense of union and stability. The encapsulation of the humerus head is lax so that there can be extensive and free movement of the arm. Neither the configuration of the articulating surfaces nor the disposition of the articular capsule furthers stability. The articular capsule, however, does include other elements which tend to stabilize the glenohumeral joint. These include various ligaments which fully or partially span the joint. The greatest stability for the glenohumeral joint is provided by the muscle groups which cross the joint and produce some of its movements. Four muscles approach the joint from the scapula. The subscapularis muscle passes in front of the joint. The supraspinatus crosses the joint superiorly. The infraspinatus muscle extends behind the joint. The teres minor muscle similarly is located posterior to the joint. These muscles and their tendons form a partly muscular, partly tendinous hood or cuff about the capsule that invests its anterior, superior, and posterior surfaces. The close investment of the capsule by these muscles and tendons has led to their designation as the musculotendinous cuff of the shoulder joint. These muscles hold the humerus to the glenoid fossa, strengthen the capsule, and flexibly resist undue movements of the humeral head in anterior, superior, and posterior direction. Since all these muscles produce rotations of the humerus, the functional structure is also referred to as the rotator cuff. Other muscles contribute lesser degrees of stability to the joint.
The movements of the shoulder joint, which are increased by associated movement of the scapula, are movements of the upper torso. The major movements occurring at the shoulder joint include:
1. Flexion in which the humerus is brought forward beside the thorax. Continued flexion carries the humerus upward as well as forward and, finally, upward and backward beside the head to a vertical position.
2. Extension in which the humerus is returned from any position of flexion to the anatomic position or is carried backward from the position beside the thorax.
3. Abduction in which the humerus moves laterally away from the body. Continued abduction carries the humerus upward as well as laterally and, finally, upward and medially to a vertical position beside the head.
4. Adduction in which the humerus is returned to the side of the body from any degree of abduction. The thorax prevents further movement toward the midline of the body, but if adduction is combined with partial flexion the arms can be carried across the front of the chest and crossed. Since the glenoid fossa faces forward as well as laterally, a similar combination of adduction and extension is less free, but the same effect can be obtained by bending of the elbows as in clapping of the hands behind the back.
5. Rotations in which the anterior aspect of the humerus turns medially (medial and internal rotation) or laterally (lateral or external rotation). Rotations combine with other movements. For example, medial rotation occurs with and facilitates full flexion to the vertical position, and lateral rotation occurs increasingly with abduction to the vertical position.
6. Combined movements in which several movements occur simultaneously or progressively are the basis of most natural motions at the shoulder joint. Circumduction, as a joint movement in general, is defined in terms of the shoulder joint. Lateral rotation of the scapula turns the glenoid fossa upward to make possible full abduction of the shoulder joint. Otherwise the humerus would impinge upon the acromion to stop the movement. Retraction of the scapula carries the glenoid fossa backward and turns it more laterally to facilitate extension of the shoulder joint. Protraction of the scapula occurs with shoulder flexion to turn the glenoid fossa forward.
In view of the structure of the glenohumeral joint, in the exercise of the upper torso, it is of paramount importance that the exercise not irritate, nor exacerbate an existing irritation or weakness in the shoulder joint. In like manner, the exercise should not cause the shoulder joint to be subjected to unnatural movements. In this respect, it is particularly important that the shoulder joint not be exposed to undue stress or strain at or near the natural limits of the range of motion of the joint.
In the prior art, it has been proposed and practiced that exercise of the muscles of the upper torso may be accomplished employing mechanical exercise devices such as the barbell, hand barbells, flye machines, various vertical lifting or pull-down devices, and the like. For example, in the barbell snatch exercise, the person grasps the barbell with their hands at spaced apart locations on the bar, and then proceeds to "snatch" the barbell from the floor and lift it above the head. The hands remain in firm gripping relationship to the bar during the exercise, thereby requiring the shoulder joint (and the elbow and wrist joints) to rotate. Due to the spaced-apart locations of the hands, these rotational movements are unnatural and great strain is placed upon the shoulder, elbow and wrist joints.
Bench pressing is another of the prior art techniques employed in exercising of the upper torso muscles. Again, in bench pressing, the hands of the person are "fixed" at spaced apart locations on the barbell, so that as the arms are moved through their paths of movement as the barbell is lifted and lowered, there occurs unnatural rotational movement of the upper limb joints. A vast majority of the persons performing the bench press (whether using a barbell or one of the more recent push-pull mechanical exercise devices) begin the press at a position in which the barbell is touching the chest. In this position, this majority of persons has a rib cage thickness-arm length ratio that requires excessive motion at the shoulder joint to touch the bar to the chest. In this position of the barbell, the mechanical advantage for the pectoralis major is dramatically decreased due to a decrease, or even non-existent force angle of the muscle.. In fact, throughout a majority of the motion occasioned by this exercise, the bar is lowered by the pectoralis major to a position where it has little or no mechanical ability, and consequently, the shoulder joint strength range is violated.
Chest press machines, like a barbell, require a fixed hand placement that does not allow for the complete motion of horizontal adduction. Also, the arc of motion made by the machine may actually take away from the movement of the pectoralis muscles.
Exercises performed with individually hand-held dumbbells can eliminate unnatural rotation, or lack of proper rotation, of the upper limb joints. Dumbbell presses or flyes allow full horizontal adduction, but at the top of the movement, or at a fully adducted position, there is no resistance against the pectoralis, for example. With free weights such as dumbbells, there is maximum resistance at the point in full horizontal abduction where the pectoralis muscle is mechanically less effective. The exercise further encourages motion beyond anatomical and mechanical limits. So-called "pec decks" and flyes present further problems in that the axes of these machines are either too narrow or too far anterior to the glenohumeral joint and tend to pull the user into unwanted protraction. Also, with these machines, the shoulder is positioned at 90 degrees of external rotation and 90 degrees of abduction. This is an extremely compromising position for the glenohumeral joint, especially when moving posterior to the frontal body plane.